Resolution and sensitivity of electron backscattered diffraction in a cold field emission gun SEM

The tradeoff between sensitivity and spatial resolution is inherent in all analytical techniques. Electron backscattered diffraction (EBSD) in a scanning electron microscope (SEM) is no exception, and determining this tradeoff for EBSD is the focus of this contribution. Because the specimen is tilted in EBSD (typically at 70°), the spatial resolution needs to be defined with respect to three orthogonal directions; as lateral resolution (within the specimen plane but normal to beam direction), longitudinal resolution (within the specimen plane but parallel to beam direction) and depth resolution (extent of depth information). The significance of these different resolution criteria becomes relevant for interface analysis, and is demonstrated using a variety of materials systems and electron-optical parameters. The sensitivity of EBSD is directly related to the ability of backscattered electrons (BSEs) to produce sufficient contrast in the Kikuchi pattern at the recording medium (phosphor in our case). The various parameters which govern the sensitivity of EBSD are discussed with the help of experimental analysis. It is argued that EBSD/OIM is a viable technique even in a cold field emission gun SEM, where there is less absolute current available and stability of current is less than for other electron sources.